Reference for Shevuot 7:1
כָּל הַנִּשְׁבָּעִין שֶׁבַּתּוֹרָה, נִשְׁבָּעִין וְלֹא מְשַׁלְּמִין. וְאֵלּוּ נִשְׁבָּעִין וְנוֹטְלִין, הַשָּׂכִיר, וְהַנִּגְזָל, וְהַנֶּחְבָּל, וְשֶׁכְּנֶגְדּוֹ חָשׁוּד עַל הַשְּׁבוּעָה, וְהַחֶנְוָנִי עַל פִּנְקָסוֹ. הַשָּׂכִיר כֵּיצַד, אָמַר לוֹ תֶּן לִי שְׂכָרִי שֶׁיֵּשׁ לִי בְיָדֶךָ, הוּא אוֹמֵר נָתַתִּי, וְהַלָּה אוֹמֵר לֹא נָטַלְתִּי, הוּא נִשְׁבָּע וְנוֹטֵל. רַבִּי יְהוּדָה אוֹמֵר, עַד שֶׁתְּהֵא שָׁם מִקְצָת הוֹדָאָה. כֵּיצַד, אָמַר לוֹ תֶּן לִי שְׂכָרִי חֲמִשִּׁים דִּינָר שֶׁיֵּשׁ לִי בְיָדֶךָ, וְהוּא אוֹמֵר הִתְקַבַּלְתָּ דִינַר זָהָב:
All of those who are besworn by Torah mandate swear and do not pay. [The Torah did not mandate that the claimant swear and take, but that the claimee swear and not pay, it being written (Exodus 22:10): "And its master shall take it, and he shall not pay" — He who is being asked to pay takes the oath.] And these swear and take [The sages ordained that they swear and take. They are all explained later in the Mishnah:] a hired laborer, one who has been robbed, one who has been struck, one whose opposite is not trusted to take an oath, and a shopkeeper over his ledger. A hired laborer — how so? [The sages ordained that a hired laborer swear and take; for the employer is busy with his workers and may not remember. This, when he claims within the prescribed time: a day-laborer, all of the night following, and a night-laborer, all of the day following. But if he claimed after his time, the employer takes a shvuath heseth that he paid him and he is exempt. Also, if he did not hire him in the presence of witnesses, the hired laborer does not swear and take. For since he can tell him: "I never hired you," he can also tell him: "I hired you and I paid you."] If he said to him: "Give me the pay that you owe me" — If the other said: "I gave it to you," and he: "I did not receive it," he (the hired laborer) swears and takes it. [But if the laborer said to him: "You stipulated that you would give me two," and the employer: "I stipulated only one," the employer swears a Torah mandated oath that it is as he says, and he gives him only one.] R. Yehudah says: (He does not swear) unless there is partial admission. How so? As when he said: "Give me my pay, fifty dinars, that you owe me," and the other said: "You received a golden dinar (twenty-five silver dinars)." [The halachah is not in accordance with R. Yehudah, neither in the instance of a hired laborer, nor in that of one who has been robbed or beaten.]